fig2

Figure 2. (A) Absorber layer thickness versus the absorption efficiency of the absorber layer 2 (A_InGaAs,x); (B) Absorptance and reflectance spectra of the grid UTC-PD with L_ab = 200 nm. A_InGaAs,x denotes the absorption efficiency of the absorber layer-2, A_metal,x denotes the absorption efficiency of the metal, and R_x denotes the reflectance of x-polarized light; (C) A_InGaAs,x of the grid UTC-PD and mesa UTC-PD; (D) A_InGaAs,x spectra for different thicknesses of collector layer 5 (L_collector); (E) Thickness of layer 5 versus A_InGaAs,x; (F) Field distributions in the x-y cross-section at the middle of the absorber layer of 2 × 2 grid units; L_ab = 200 nm, L_collector = 400 nm. The white dotted box outlines enclosed air; the rest of the area includes the detectors; (G and H) Field distributions in the x-z cross-section at the black line and the x-z cross-section at the red line. Inside the red dotted box is the absorber layer. Inside the yellow dotted box is the metal; (I and J) Field distributions in the x-z cross-section inside the grid device; L_ab = 200 nm, L_collector = 820 nm. Inside the red dotted box is the absorber layer. Inside the yellow dotted box is the metal. UTC-PD: Uni-traveling-carrier photodiode; L_ab: thickness of the absorber layer.